1. Field of the Invention
The invention relates to digital voice signal transmission circuits employing delta-modulation coding and decoding.
2. Statement of the Problem
In long haul transmission circuits for telephone communication the transmission channel may be intermittently interrupted, either for echo cancellation purposes or to permit time multiplex handling of other transmissions. It is well known, however, that total disconnection causes an unnatural and disconcerting reception effect of total silence giving the listener the impression that the connection has been broken.
In certain analog systems the problem is avoided by loss insertion. Instead of completely disconnecting the channel a high loss (e.g. 50 db) is switched into the transmission path. However, it is believed that this technique has not hitherto been applicable to a digital voice signal channel employing delta-modulation coding.